The present invention relates to a flotation cell with one or more edges for removing froth and with a rotor and stator meant to be immersed in the liquid to be flotated.
Froth flotation is commonly used, for example, in mineral concentration technology for the separation of valuable minerals from reject matte and in the regeneration of waste paper for the separation of inks from waste-paper pulp. The flotation technique is based on the selective property of finely ground mineral or other surfaces, in a liquid, to adhere to the surface of a gas bubble, usually air, while the other particles do not; this property can be natural or produced artificially by chemical means.
Flotation is usually performed by means of an apparatus called a flotation cell. Its purpose is to produce gas-liquid interfaces, to contact the particles with them, i.e., bubbles, and to separate accept and reject particles from each other. The particles adhering to the gas bubbles form a froth on the slurry surface in the cell. In conventional cells the removal of the froth from the cell is performed by means of separate froth skimmers, or the froth layer may be so thick that the froth flows, under the effect of gravity, over the froth removal edge.
In the most commonly used flotation cells, air is dispersed into the slurry, and the slurry is mixed by means of a rotor revolving about a vertical shaft. The air is fed through the shaft and rotor or through separate nozzles. The rotor is concentric with the stator surrounding it. In this case, the flow pattern in a mixing vessel (flotation cell) concentric with the stator-rotor system is labile; mixing flows rise to the surface at different spots and the surface flow has no definite direction. In some cell types attempts have been made to quide the flows by means of baffles.
The object of the present invention is to provide a flotation cell of the above type, but with a possibility of controlling and regulating the surface flow in the desired direction within the cell by means of the pumping effect of the rotorstator system.